Overview
P.02 on a Vaillant ecoTEC Plus usually indicates the boiler has entered a test/program mode related to minimum load or low‑flame checks. On older ecoTEC models P.00, P.1 and P.2 (or P.02) are used for pump purge, high flame and low flame/test routines. In many cases P.02 is not a conventional fault code but a diagnostic state used during commissioning or service to check how the boiler behaves at low firing rates. If P.02 appears unexpectedly or the boiler shuts down or shows safety cut‑out messages while in or after this mode, it can point to underlying issues that prevented normal operation during the test — for example sensor faults, poor circulation (pump/diverter valve or air in the system), low water pressure, or ignition/flame detection problems. Severity varies: if the code is shown because someone has deliberately started a test it is low severity; if it recurs or is accompanied by loss of heating/hot water, fault codes (F‑codes), or smells of gas then treat it as more serious and get professional help. This is mainly a job for a qualified Gas Safe engineer, though there are a few safe initial checks a homeowner can perform.
Possible Cause: Minimum load test program
Troubleshooting Steps
Safety precautions:
- If you smell gas, open windows, do not operate electrical switches, leave the property and call your gas emergency number immediately.
- Before doing any checks, make sure the boiler’s electrical supply and the gas isolator cock are on. Do not remove covers or attempt internal repairs — live components and gas parts are dangerous.
Initial homeowner checks (safe, simple checks you can do):
1. Look at the boiler display and note the exact message. If it simply shows P.02 and the boiler is running normally (heating/hot water available), it may just be a test mode active and not an emergency.
2. Ask whether the boiler was recently serviced or an installer was on site — P.02 can be entered during service. If so, the installer may have left it in a test mode.
3. Check the system pressure gauge on the boiler. Normal operating pressure is usually around 1–1.5 bar when cold. If the pressure is low (well below 1.0 bar) top up the system using the filling loop following the boiler manual. If you are not comfortable doing this, stop and call an engineer.
4. Check that external controls/thermostats and programmers are calling for heat. Set the programmer to demand heating or hot water to see if the boiler responds.
5. Try a simple reset: press the boiler’s reset/fault clear button for one second (or follow the manual). If P.02 disappears and the boiler returns to normal, monitor for recurrence.
Diagnostic and next steps (do not open the boiler or attempt gas/electrical repairs):
1. If the code appeared after you or someone pressed buttons, it may be a deliberate test mode. To exit, use the normal reset procedure or switch the boiler off at the mains for 30 seconds and back on; if it returns to normal, no further action may be needed.
2. If P.02 stays displayed, or the boiler shuts down to a fault (for example F.22 low water pressure, F.20/ F.29 flame/ignition related codes, or any SCO safety message), record all displayed codes and times. These details are useful to the engineer.
3. Check for circulation: feel the flow and return pipes when the boiler is calling for heat (careful, they can be hot). If one pipe is much cooler than the other or the boiler makes unusual noises, the pump may be blocked or not running, or there may be air in the system. Bleed radiators if you suspect air and recheck pressure afterward.
4. If the boiler displays additional fault codes related to sensors (flow/return), water pressure, or flame detection, do not attempt sensor or gas valve repairs. These faults often require testing wiring connectors, sensor resistances and electronic checks that need a Gas Safe engineer and specialist tools.
5. If you have repeatedly attempted resets and the boiler still shows P.02 or other faults, or if you have no heating/hot water, arrange a service visit from a Gas Safe registered engineer. Give them the exact display texts and any steps you’ve already taken.
When to call a professional immediately:
- Any smell of gas or suspicion of a gas leak.
- Boiler will not ignite or there is persistent loss of flame or repeated safety cut‑outs.
- You cannot restore normal heating/hot water after basic checks and a reset.
- The code recurs after a service or accompanies other fault codes indicating sensors, pump, diverter valve or gas/ignition issues.
Final note: P.02 is often a test/program mode and can be harmless if intentionally used during servicing, but persistent or unexpected appearance of the code, especially with other fault indicators or loss of heating/hot water, requires a qualified Gas Safe engineer. Do not attempt internal electrical, gas or combustion component repairs yourself.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Vaillant EcoTEC Plus Gas Boiler.